For years, many companies in Japan have required women to wear high heels to the office.

In her tweets, Ishikawa coined the hashtag #KuToo, which is both a play on two Japanese words -- "kutsu," meaning shoes, and "kutsuu," meaning pain -- and a pun on the #MeToo hashtag, which represents an international movement against sexual harassment.

#KuToo has since been used by women to talk about their experiences on social media.

An official at Japan's Ministry of Health, Labor and Welfare's equal employment opportunity division said it had no plans to change the rules around whether employers could require staff to wear certain clothes or shoes. There are currently no laws that restrict companies from regulating employees' work wear.

The official noted that men were also subject to rules, as they were often required to wear ties and leather shoes. "If common sense or ideas about manners in society change, the rules might be subject to change," said the official.

The #KuToo movement in Japan follows a similar campaign in the UK in 2016, where more than 100,000 people signed a petition calling for a ban on company dress codes which force women to wear heels at work.

In recent years, campaigns such as #MeToo have brought Japan's gender inequality problems into the spotlight. Japan is ranked at 110 out of 149 countries in the World Economic Forum's index measuring the degree of gender equality.

The country ranks bottom among the G7 countries for gender equality, despite Prime Minister Shinzo Abe's pledge to empower working women through a policy called "womenomics."